Process for coating detergent tablets

Abstract

A process for coating laundry detergent or cleaning product tablets that contain builder(s) and also, if desired, further laundry detergent and cleaning product ingredients, by transporting the tablets on a conveyor belt provided with a multiplicity of apertures and forcing coating material through the conveyor belt apertures from below with a force such that the coating material forced over the conveying plane forms a surge through which the tablets are transported.

What is claimed is:  
     
       1. A process for coating laundry detergent or cleaning product tablets that comprise builder(s) and also, if desired, further laundry detergent and cleaning product ingredients, said process comprising the steps of transporting the tablets at a speed in a conveying plane on a conveyor belt provided with a multiplicity of apertures and forcing coating material through the conveyor belt apertures from below with a force such that the coating material forced over the conveying plane forms a surge through which the tablets are transported and wherein the coating material is applied in the form of a solution or dispersion or in the form of a melt. 
     
     
       2. The process of  claim 1 , wherein the tablets additionally pass through a mist of coating material. 
     
     
       3. The process of  claim 1 , wherein the surge or coating material lifts the tablets from the conveyor belt. 
     
     
       4. The process of  claim 1 , wherein the surge is generated by a roller which rotates in the coating material, the movement of the surge being generated in the direction of the conveying direction of the tablets. 
     
     
       5. The process of  claim 4 , wherein return flow of the coating material is adjusted by way of a slide valve which is adjustable tangentially in the direction of the roller. 
     
     
       6. The process of  claim 1 , wherein the surge has a speed on emergence from the apertures that is approximately the same as the speed of the conveyor belt. 
     
     
       7. The process of  claim 1 , wherein the coating material comprises water-soluble and/or meltable polymers or polymer mixtures. 
     
     
       8. The process of  claim 7 , wherein the polymers or polymer mixtures comprise one or more of: 
       a) water-soluble nonionic polymers selected from the group consisting of  
       a1) polyvinylpyrrolidones  
       a2) vinylpyrrolidone-vinyl ester copolymers  
       a3) cellulose ethers  
       a4) homopolymers of vinyl alcohol, copolymers of vinyl alcohol with copolymerizable monomers, or hydrolysis products of vinyl ester homopolymers or vinyl ester copolymers with copolymerizable monomers  
       b) water-soluble amphoteric polymers selected from the group consisting of  
       b1) alkylacrylamide-acrylic acid copolymers  
       b2) alkylacrylamide-methacrylic acid copolymers  
       b3) alkylacrylamide-methylmethacrylic acid copolymers  
       b4) alkylacrylamide-acrylic acid-alkylaminoalkyl-(meth)acrylic acid copolymers  
       b5) alkylacrylamide-methacrylic acid-alkylamino-alkyl(meth)acrylic acid copolymers  
       b6) alkylacrylamide-methylmethacrylic acid-alkyl-aminoalkyl(meth)acrylic acid copolymers  
       b7) alkylacrylamide-alkyl methacrylate-alkylaminoethyl methacrylate-alkyl methacrylate copolymers  
       b8) copolymers of  
       b8i) unsaturated carboxylic acids  
       b8ii) cationically derivatized unsaturated carboxylic acids  
       b8iii) if desired, further ionic or nonionic monomers  
       c) water-soluble zwitterionic polymers selected from the group consisting of  
       c1) acrylamidoalkyltrialkylammonium chloride-acrylic acid copolymers and their alkali metal and ammonium salts  
       c2) acrylamidoalkyltrialkylammonium chloride-methacrylic acid copolymers and their alkali metal and ammonium salts  
       c3) methacroylethyl betaine-methacrylate copolymers  
       d) water-soluble anionic polymers selected from the group consisting of  
       d1) vinyl acetate-crotonic acid copolymers  
       d2) vinylpyrrolidone-vinyl acrylate copolymers  
       d3) acrylic acid-ethyl acrylate-N-tert-butylacrylamide terpolymers  
       d4) graft polymers of vinyl esters, esters of acrylic acid or methacrylic acid alone or in a mixture, copolymerized with crotonic acid, acrylic acid or methacrylic acid with poly-alkylene oxides and/or polyalkylene glycols  
       d5) grafted and crosslinked copolymers from the copolymerization of  
       d5i) at least one monomer of the nonionic type,  
       d5ii) at least one monomer of the ionic type,  
       d5iii)polyethylene glycol, and  
       d5iv) a crosslinker  
       d6) copolymers obtained by copolymerizing at least one monomer from each of the three following groups:  
       d6i) esters of unsaturated alcohols and short-chain saturated carboxylic acids and/or esters of short-chain saturated alcohols and unsaturated carboxylic acids,  
       d6ii) unsaturated carboxylic acids,  
       d6iii) esters of long-chain carboxylic acids and unsaturated alcohols and/or esters of the carboxylic acids of group d6ii) with saturated or unsaturated, straight-chain or branched C 8-18  alcohol  
       d7) graft copolymers obtainable by grafting d7i) polyalkylene oxides with d7ii) vinyl acetate  
       d8) terpolymers of crotonic acid, vinyl acetate and an allyl or methallyl ester  
       d9) tetra- and pentapolymers of  
       d9i) crotonic acid or allyloxyacetic acid  
       d9ii) vinyl acetate or vinyl propionate  
       d9iii) branched allyl or methallyl esters  
       d9iv) vinyl ethers, vinyl esters or straight-chain allyl or methallyl esters  
       d10) crotonic acid copolymers with one or more monomers from the group consisting of ethylene, vinylbenzene, vinyl methyl ether, acrylamide and water-soluble salts thereof  
       d11) terpolymers of vinyl acetate, crotonic acid and vinyl esters of a saturated aliphatic α-branched monocarboxylic acid  
       e) water-soluble cationic polymers selected from the group consisting of  
       e1) quaternized cellulose derivatives  
       e2) polysiloxanes with quaternary groups  
       e3) cationic guar derivatives  
       e4) polymeric dimethyldiallylammonium salts and their copolymers with esters and amides of acrylic acid and methacrylic acid  
       e5) copolymers of vinylpyrrolidone with quaternized derivatives of dialkylaminoacrylate and -methacrylate  
       e6) vinylpyrrolidone-methoimidazolinium chloride copolymers  
       e7) quaternized polyvinyl alcohol  
       e8) polymers indicated under the INCI designations Polyquaternium 2, Polyquaternium 17, Polyquaternium 18, and Polyquaternium 27  
       f) polyurethanes  
       g) lower critical separation temperature (LCST) polymers, preferably alkylated and/or hydroxyalkylated polysaccharides, cellulose ethers, acrylamides, such as polyisopropylacrylamide, copolymers of acrylamides, polyvinylcaprolactam, copolymers of polyvinylcaprolactam, particularly those with polyvinylpyrrolidone, polyvinyl methyl ether, copolymers of polyvinyl methyl ether, and blends of these substances.  
     
     
       9. The process of  claim 1 , wherein the coating material has a temperature of from 30 to 300° C. 
     
     
       10. The process of  claim 1 , wherein the coating material is applied in the form of an aqueous solution or dispersion, and the tablets are subsequently subjected to a drying step. 
     
     
       11. The process of  claim 1 , wherein the weight ratio of uncoated tablet to coating is >10:1. 
     
     
       12. The process of  claim 1 , wherein the thickness of the coating on the tablet is from 0.1 to 500 μm. 
     
     
       13. The process of  claim 1 , wherein the coating additionally comprises substances selected from the groups consisting of disintegration aids, dyes, optical brighteners, fragrances, enzymes, bleaches, bleach activators, silver protectants, complexing agents, surfactants, graying inhibitors, and mixtures thereof in total amounts of from 0.5 to 30% by weight based on the weight of the coating. 
     
     
       14. The process of  claim 9 , wherein the coating has a temperature of from 35 to 90° C. 
     
     
       15. The process of  claim 14 , wherein the coating has a temperature of from 40 to 85° C. 
     
     
       16. The process of  claim 15 , wherein the coating has a temperature of from 50 to 80° C. 
     
     
       17. The process of  claim 11 , wherein the weight ratio of uncoated tablet to coating is >25:1. 
     
     
       18. The process of  claim 17 , wherein the weight ratio of uncoated tablet to coating is >50:1. 
     
     
       19. The process of  claim 12 , wherein the thickness of the coating on the tablet is from 0.5 to 250 μm. 
     
     
       20. The process of  claim 19 , wherein the thickness of the coating on the tablet is from 5 to 100 μm. 
     
     
       21. The process of  claim 13 , wherein the coating is present in total amounts of from 1 to 20% by weight based on the weight of the coating. 
     
     
       22. The process of  claim 21 , wherein the coating is present in total amounts of from 2.5 to 10% by weight, based on the weight of the coating.